1. Field of the Invention
This invention relates to a film magazine for a roll film, and more particuarly to a film magazine for a roll film having cylindrical shape which is provided with film speed indicating means to be sensed by a film speed sensing means equipped in a photographic camera.
2. Description of the Prior Art
As disclosed in U. S. Pat. No. 2,492,928, it has been known in the art to provide on the outer surface of a film magazine of cylindrical shape an electric contact member for short-circuiting a resistor provided in a diaphragm control circuit comprising a diaphragm control means, a photocell and a power source. The size or length of the electric contact member provided on the outer surface of the film magazine is determined with respect to the film speed of the film loaded in the film magazine so that a part of the resistor may be short-circuited to drive the diaphragm control means by the degree corresponding to the brightness of the object to be photographed measured by the photocell. In order to sense the length of the electric contact member and short-circuit the resistor by the length corresponding to the film speed, there are a number of electric brushes provided in the camera body to be put into contact with the electric contact member. The number of electric brushes occupy a large space in the camera body and make it difficult to effect uniform electric contact between the number of brushes and the contact member. Owing to the uneven contact between the brushes and the contact member, malfunction of the diaphragm control means will often occur.
Further, since the electric contact member provided on the surface of the conventional film magazine for indicating the film speed of the film loaded therein is made of metal plate and is adhered to or partly buried on the surface of the film magazine, the number of processes in the manufacture of the film magazine is increased and the cost of manufacture thereof is increased by the expensive metal material.
In addition, in the conventional film magazine provided with the metal contact member on the outer surface thereof is disadvantageous in that the surface of the contact member is apt to be stained by the sweat of fingers or the like. The stains on the surface of the contact member will often cause malfunction of the electric circuit for controlling the diaphragm.